<?php


function test($i)
{
    switch ($i) {
        case 1:
        case 2:
        case 3:
            echo 'param ', $i, "\n\r";
            break;
        case 4:
            echo 'other ', $i, "\n\r";
        default:
            echo 'default ', $i, "\n\r";
    }
}

for ($i = 0; $i < 6; $i++) {
    test($i);
}


//$ww = -00000001-00000001-00000000;

$merchantParams = [];
$delivery = 333;
$return = 222;
$refund = 0;
!empty($delivery) && $merchantParams['delivery'] = $delivery;
!empty($return) && $merchantParams['return'] = $return;
!empty($refund) && $merchantParams['return'] = $refund;

var_dump($merchantParams);